Open heart surgery has become one of the most common surgical procedures performed in the United States. During the process of opening the chest cavity to perform the surgery, a vertical incision is made through the skin over the breast bone (sternum) and the breast bone is then cut vertically with a surgical saw. The surgeon then gains access to the pericardial area by spreading the cut edges of the bone with a sternal retractor.
The spreading of the rib cage with the sternal retractor places great pressure on the ribs, and when the pressure becomes too great, the ribs can break. The shorter ribs, with their smaller radius, are more likely to break than the longer ribs in the middle or lower area of the rib cage. In addition to the pain caused by the broken ribs in the chest wall area after surgery, the ribs tend to break in an area in which the broken ends of the bone exert pressure against, or impale, the nerves which innervate the arms as they leave the spinal column. In approximately five to ten percent of open heart patients, these nerves are damaged by the retraction of the rib cage.
It has been suggested that the sternal retractor be placed in the cut so as to bear only against the lower two-thirds of the breast bone, thus placing less stress on the smaller, upper ribs. Placement of the retractor on the lower portion of the sternum does result in fewer broken ribs, but it places uneven pressure on the sternum itself, often resulting in breakage of the sternum. The breakage of the sternum causes increased blood loss during the surgery and presents complications because the sternum occasionally does not heal properly, often necessitating another operation at a later date.
There are a number of retractors available that are presently in use as sternal retractors. The Codman retractor consists of a cross-bar with two arms attached, one of which can be ratcheted along the length of the cross-bar to retract the rib cage. The arms are provided with detachable blades hooked to the arms by hooks which project down into the incision. The Cooley and Ankeney retractors are similar in that they also consist of cross-bars and arms, one or more of which is ratcheted along the cross-bar to retract the incision. They differ from each other, and from the Codman retractor, in the configuration of the blades which contact the incision, bearing against the sternum to retract the rib cage. The Burford-Finochietto rib spreader is provided with two arms which are racheted along the cross-bar and interchangable blades for contacting the sternum. The Finochietto rib spreader is similar but with only one movable arm. The Lemmon sternal spreader is provided with one arm which can be ratcheted along the cross-bar and the blades are modified to better retain the edges of the sternum while the rib cage is being retracted.
However, all of these prior art retractors open the rib cage in a more or less rectangular manner (i.e., they move the cut edges of the sternum away from each other while keeping them parallel to each other). The rectangular shape of the opening causes the uneven pressure on the ribs because the rib cage is not rectangularly shaped, and the result is the breakage of the smaller ribs. There is, therefore, a need for a retractor which distributes even pressure along the edges of the breast bone without exerting a great amount of pressure on the smaller ribs at the top of the rib cage.
It is an object of the present invention to provide a sternal retractor which is capable of distributing the force exerted on the rib cage evenly along the length of the incision. Another object of the present invention is to provide a sternal retractor which can be used to retract the rib cage without breaking the ribs. Another object of the present invention is to provide a retractor capable of retracting the rib cage in a triangularly-shaped opening.
Another object of the present invention is to provide a sternal retractor with pivoting arms, at least one of which can be moved along a cross-bar so as to retract the rib cage. Another object of the present invention is to reduce the damage to the nerve tissue caused by the broken ends of the ribs which may be broken during retraction of the rib cage for open heart surgery.